The present invention relates to a method and apparatus for conditioning tobacco. More particularly, the invention relates to improvements in a method and apparatus for contacting particles of tobacco with additives to thus change the condition and/or characteristics of tobacco particles. Still more particularly, the invention relates to improvements in a method and apparatus for producing a homogeneous mixture of tobacco particles and one or more types of comminuted solid, liquid and/or gaseous additives.
Prior to being fed into a processing machine to be converted into cigarettes, cigars, cigarillos, pipe tobacco or cheroots, particles of tobacco are normally subjected to one or more treatments which usually involve conditioning and comminuting or cutting. The conditioning of tobacco includes the admission of various additives such as moisture in the form of steam, vapors or water, liquid aromatic or flavoring substances and/or pulverulent additives.
Particles of tobacco are normally conditioned in slightly inclined hollow rotary drums, known as moistening, casing or flavoring drums. The axes of drums are inclined downwardly in the direction of transport of tobacco therethrough and their inlet ends receive tobacco particles in the form of whole leaves, tobacco leaf laminae, tobacco shreds, fragments of reconstituted tobacco, fragments of or entire ribs and/or a mixture of two or more types of tobacco particles. Such particles are caused to pass through and toward the discharge end of the revolving drum to be contacted by additives which are discharged by one or more atomizing, spreading or analogous supplying devices installed in the interior of the drum and normally at a level above the path for the tobacco particles. The nature of additive supplying devices depends on the type of additives; for example, the supplying devices may be steam discharging nozzles, nozzles which discharge atomized flavoring agents, casing agents, water and/or other liquids, and/or revolving wheels for uniform distribution of pulverulent additives. The nature of finely distributed additives depends on their composition, i.e., the additives may be minute globules of liquid, aerosols, solid particles or gases. The region in which the particles of tobacco passing through the revolving drum are contacted by additives is called the contact zone.
The revolving drum is further provided with internal entraining means in the form of heating or cooling pipes, paddles, blades, ribs or the like which serve to turn and/or agitate the travelling particles to thus promote contact between additives and all sides of the particles. It was found that such mode of agitating tobacco particles in a revolving drum does not insure uniform contact of additives with all sides of each particle because the turning action of blades, coils, paddles or like mechanical devices is neither uniform nor capable of insuring satisfactory agitation of each and every particle during travel from the inlet to the discharge end of the drum. Therefore, a substantial percentage of additives, particularly atomized liquids, invariably misses the tobacco particles and deposits on the internal surface of the drum.